Study On Aerothermodynamic Performance Of Turbine For Micro Gas Turbine Based On Multi Component Coupling

As a major member of distributed energy,micro gas turbines are an important way to achieve the goals of “carbon peak” and “carbon neutral”.It is also one of the main frontier disciplines of fluid mechanics in contemporary turbomachinery.Moreover,it has the characteristics of small size,compact structure,diversity of fuels,low exhaust emissions,and high efficiency under combined cooling,heat and power generation.The characteristics of small scale and high compactness lead to significant coupling flow between the turbine and other components.The inlet and outlet of turbine are respectively connected to the outlet of combustion chamber and to the inlet of regenerator through a connection section.For miniaturized combustion chambers,the length of the main combustion zone and the mixing zone is insufficient.The gas flow entering the flame tube through the air hole and the evaporation tube is difficult to fully mix and rectify,which worsens the non-uniformity of flow field at the turbine inlet.The turbine exhaust gas flows into the regenerator through the transition section with a certain swirl,which increases the inlet non-uniformity of the regenerator and increases the pressure loss of the regenerator.This results in changes in the turbine outlet flow field.These factors have an important impact on the aerodynamic and thermodynamic performance of the turbine and the thermodynamic cycle performance of the entire machine,and are one of the main design challenges faced by micro turbines to achieve high efficiency.According to the radial flow turbine widely used in micro gas turbines,a three-dimensional numerical simulation method for the turbine coupled with the regenerator and combustion chamber is developed based on the porous media model of regenerator and turbine obtained by comprehensive design method considering wall heat transfer.The aerodynamic and thermodynamic performance of micro radial inflow turbine with multi component coupling is investigated.Firstly,a full temperature and full speed test rig for the micro radial inflow turbine is established using a screw air compressor as the air source,a kerosene combustion chamber as the heat source,a centrifugal compressor as the load,and an oil film bearing as the rotor system.An innovative arrangement of pressure and temperature probes at the micro radial inflow turbine inlet is proposed based on the fact that the leading edge of the guide blade is facing the incoming flow direction.A wall heat transfer control strategy between the compressor and the turbine is established to reduce the non-uniformity of the flow field distribution at the turbine inlet and the heat loss in the volute.Secondly,a comprehensive design method considering wall heat transfer for micro radial inflow turbine is proposed based on a one-dimensional mean-line model and non-adiabatic thermodynamic process.Combining the thermodynamic process of a conventional radial inflow turbine with the aerodynamic characteristics of a radial inflow turbine considering heat transfer,a thermodynamic cycle of a micro radial inflow turbine considering wall heat transfer is assumed.The design parameter relationship between thermal insulation and consideration of wall heat transfer for micro radial inflow turbines is established.A comprehensive design method for micro radial inflow turbines considering wall heat transfer is proposed based on the traditional design process and empirical formulas for radial inflow turbines.The results show that the maximum deviations between the comprehensive design method considering wall heat transfer and the test data,as well as between the traditional adiabatic design method and the test data,are 2.71% and 3.53%,respectively.At the same time,the research on turbine aerodynamics and thermodynamics of coupled regenerators is carried out based on the porous medium model of the heat exchange core.A geometric model and numerical simulation method for the heat exchange core are developed to deeply explore the heat exchange and flow resistance characteristics of the regenerator.Moreover,a method for calculating the pressure drop loss of the heat exchange core is proposed.A porous medium model of the regenerator is established to develop a turbine numerical simulation method coupled with the regenerator.The research results show that the deviations between the Nusselt number calculated by the numerical model of heat exchange core and the porous medium model and the fanning friction factor are 3.6% and 10.6%,respectively.The turbine performance of the coupled regenerator is significantly lower than that of the single turbine due to the existence of the vortex in the connection section and the uneven radial distribution of the flow field in the gas channel of the regenerator.Finally,the aerodynamic and thermodynamic performance of a micro radial inflow turbine is investigated using a turbine numerical simulation method coupled with the regenerator and combustion chamber.Based on the porous media model of regenerator and turbine model obtained by comprehensive design method considering wall heat transfer,a numerical simulation method for turbine coupled with regenerator and combustion chamber is developed.Thus,the flow field distribution characteristics at the inlet and outlet of the turbine are revealed under multi component coupling,and the aerodynamic and the thermodynamic performance and flow losses of the turbine are analyzed.The results show that the velocity and total temperature distribution at turbine inlet are significantly non-uniform along the circumferential direction,while the total pressure is relatively uniform along the circumferential direction.Moreover,there is a significant difference in the outlet flow field between a multi component coupled turbine and a single turbine.